The London skylike is famous all round the world, but apart form the tube, beneath the streets very few people know what is there. Ackroyd's book really only scratches the surface, as it is fairly short, but he uncovers litte gems of information on the 2000 year old history of London. Every time anyone digs a hole there another nugget of history is revealed. There are chapters on the tube, the hidden rivers of London, and the Fleet, which was 60 feet wide at certain points has a whole chapter to itself. There are sketchy details on the government tunnels, so of which are open to the public, and others that are still not. Some of the archeological details are fascinating, in particular the finds, and in some case still operational Roman water courses. Really enjoyed reading it, looking forward to some of his other books now.